body {
background-color: #f1f5f9;
margin: 0;
padding: 20px;
}
.lesson-container {
font-family: ‘Segoe UI’, Tahoma, Geneva, Verdana, sans-serif;
max-width: 900px;
margin: 0 auto;
background-color: #ffffff;
border-radius: 16px;
box-shadow: 0 10px 30px rgba(0,0,0,0.08);
border: 1px solid #e2e8f0;
overflow: hidden;
color: #334155;
line-height: 1.6;
}
.lesson-header {
background: linear-gradient(135deg, #1e293b, #334155);
color: white;
padding: 30px 20px;
text-align: center;
}
.lesson-header h1 {
margin: 0;
font-size: 26px;
text-transform: uppercase;
letter-spacing: 1px;
color: #f8fafc;
}
.lesson-header p {
margin: 10px 0 0 0;
font-size: 16px;
color: #cbd5e1;
}
.content-section {
padding: 30px;
}
.concept-box {
background-color: #f0fdf4;
border-left: 5px solid #22c55e;
padding: 15px 20px;
border-radius: 0 8px 8px 0;
margin-bottom: 30px;
}
.concept-box h3 {
margin-top: 0;
color: #166534;
display: flex;
align-items: center;
gap: 8px;
}

/* Styles for the Infographic */
.visual-grid {
display: flex;
flex-wrap: wrap;
gap: 20px;
justify-content: center;
margin-bottom: 20px;
}
.visual-card {
flex: 1;
min-width: 300px;
padding: 20px;
border-radius: 12px;
text-align: center;
}
.card-fe {
background: #f8fafc;
border-top: 4px solid #94a3b8;
}
.card-ni {
background: #fffbeb;
border-top: 4px solid #f59e0b;
}

/* Styles for the 4 Steps */
.step-container {
margin-top: 40px;
}
.step-header {
text-align: center;
margin-bottom: 25px;
color: #0f172a;
}
.step-grid {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
gap: 20px;
}
.step-card {
background: #ffffff;
border: 1px solid #e2e8f0;
border-radius: 10px;
padding: 20px;
box-shadow: 0 4px 6px rgba(0,0,0,0.02);
transition: transform 0.2s;
}
.step-card:hover {
transform: translateY(-3px);
box-shadow: 0 10px 15px rgba(0,0,0,0.05);
}
.step-num {
display: inline-block;
width: 30px;
height: 30px;
line-height: 30px;
text-align: center;
background: #3b82f6;
color: white;
border-radius: 50%;
font-weight: bold;
margin-right: 10px;
}
.step-card h4 {
margin-top: 0;
display: flex;
align-items: center;
color: #1e293b;
border-bottom: 1px solid #f1f5f9;
padding-bottom: 10px;
}
.math-line {
background: #f8fafc;
padding: 10px;
border-radius: 6px;
font-family: ‘Courier New’, Courier, monospace;
font-weight: bold;
color: #334155;
margin: 10px 0;
overflow-x: auto;
}
.highlight {
color: #d97706;
font-weight: bold;
}